A secondary battery having easy applicability depending on a product group and electrical characteristics such as high energy density has been generally applied to an electric vehicle (EV) and a hybrid vehicle (HV) which are driven by an electrical driving source, an energy storage system (ESS) or an uninterruptible power supply (UPS) system which uses a medium-large size battery used for a household or industrial purpose, and the like, as well as portable devices.
The secondary battery may surprisingly reduce the use of fossil fuel and does not generate by-products due to the use of energy at all and therefore has received attention as a new energy source for enhancing environmentally-friendly characteristics and energy efficiency.
When the secondary battery is implemented as a battery for a portable terminal, and the like, the secondary battery may not necessarily be like that, but the battery applied to the electric vehicle or the energy storage source as described above is generally used in a form in which a plurality of unit secondary cells is collected and thus has high suitability for high-capacity environment.
When the battery, in particular, a plurality of secondary batteries repeatedly carries out charging and discharging, it is necessary to manage the batter by efficiently controlling the charging and discharging of the battery so as to appropriately maintain the operation state and performance of the battery.
To this end, a battery management system (BMS) to manage the state and performance of the battery is provided. The BMS serves to detect the current, voltage, temperature, and the like of the battery, calculate a state of charge (SOC), equalize a cell voltage, and control a high voltage relay based on the detected current, voltage, temperature, and the like, and a high voltage relay apparatus is configured to include a current detection apparatus of the battery pack and a high voltage relay, and the current detection apparatus detects a charging and discharge current amount, transfers a value of the detected current amount to the BMS, and receives a control signal from the BMS to drive the relay.
In particular, when a normal charging current is introduced into the battery of which the voltage excessively drops at the time of the initial charging and discharging, the battery abnormally generates heat and thus a spark is generated, thereby causing damage to a switch. Therefore, it is important to drive a precharge relay switch to control the battery voltage until the battery voltage rises to some degree when a voltage conversion apparatus is connected to the battery.
Therefore, it is an essential factor to calculate the resistance value of the precharge resistor included in a precharge relay switch line in order to control the relay switch. However, according to the related art, when the precharge resistance is not specified or is unknown, the precharge resistance needs to be measured by separately disassembling the battery pack, and therefore a lot of cost and time are required, thereby causing reduction in convenience or efficiency.